Creative Director Keiichiro Toyama explained the reason, or better, mentioned that we’ll understand the reason in an interview on the Japanese magazine Weekly Famitsu.

We’ve kept you waiting for new information on Gravity Daze [Gravity Rush’s Japanese Name], but I think you’ll understand the reason for the wait when it’ll be shown to the world.

We don’t really know what kind of project Toyama-san and his team are working on, and whether it’s a sequel of Gravity Rush, a different project within the same IP or something else.

His wording could even imply a new platform, as a new title on PS4, which would require completely new assets and a fresh start from the ground up, could be the “understandable” cause for the wait. Of course that’s just my personal speculation, so take it for what it is.

We’ll have to wait longer, but considering the quality of Gravity Rush, it should definitely be worth it.